DESCRIPTION

The net80211 software layer provides a support framework for drivers that
includes comprehensive regulatory support. net80211 provides mechanisms
that enforce regulatorypolicy by privileged user applications.
Drivers define a device's capabilities and can intercept and control
regulatory changes requested through net80211. The initial regulatory
state, including the channel list, must be filled in by the driver before
calling ieee80211_ifattach(). The channel list should reflect the set of
channels the device is calibrated for use on. This list may also be
requested later through the ic_getradiocaps method in the ieee80211com
structure. The ieee80211_init_channels() function is provided as a
rudimentary fallback for drivers that do not (or cannot) fill in a proper
channel list. Default regulatory state is supplied such as the
regulatory SKU, ISO country code, location (e.g. indoor, outdoor), and a
set of frequency bands the device is capable of operating on. net80211
populates the channel table in ic_channels with a default set of channels
and capabilities. Note this mechanism should be used with care as any
mismatch between the channel list created and the device's capabilities
can result in runtime errors (e.g. a request to operate on a channel the
device does not support). The SKU and country information are used for
generating 802.11h protocol elements and related operation such as for
802.11d; mis-setup by a driver is not fatal, only potentially confusing.
Devices that do not have a fixed/default regulatory state can set the
regulatory SKU to SKU_DEBUG and country code to CTRY_DEFAULT and leave
proper setup to user applications. If default settings are known they
can be installed and/or an event can be dispatched to user space using
ieee80211_notify_country() so that devd(8) will do the appropriate setup
work at system boot (or device insertion).
The channel table is sorted to optimize lookups using the
ieee80211_sort_channels() routine. This should be done whenever the
channel table contents are modified.
The ieee80211_alloc_countryie() function allocates an information element
as specified by 802.11h. Because this is expensive to generate it is
cached in ic_countryie and generated only when regulatory state changes.
Drivers that call ieee80211_alloc_countryie() directly should not help
with this caching; doing so may confuse the net80211 layer.

DRIVERREGULATORYCONTROL

Drivers can control regulatory change requests by overriding the
ic_setregdomain method that checks change requests. While drivers can
reject any request that does not meet its requirements it is recommended
that one be lenient in what is accepted and, whenever possible, instead
of rejecting a request, alter it to be correct. For example, if the
transmit power cap for a channel is too high the driver can either reject
the request or (better) reduce the cap to be compliant. Requests that
include unacceptable channels should cause the request to be rejected as
otherwise a mismatch may be created between application state and the
state managed by net80211. The exact rules by which to operate are still
being codified.